This invention relates generally to a belt, and more particularly to a lubricated belt for use in applications such as conveying systems.
Conveying systems are used in a number of applications, particularly material handling, package handling and sortation, and the like. One such application is baggage conveying systems in airports.
A conveying system generally comprises an endless belt having a top, or outer, surface and a bottom, or inner, surface; guide rollers around which the belt passes; and spaced support rollers for supporting the belt. The belt is driven, directly or indirectly, by a motor so that the bottom surface of the belt slides across the rollers. In some conveying systems, such as systems for airport baggage handling, the support rollers are replaced by a stationary slider bed, or deck, for supporting the belt. The bottom surface of the belt slides across the upper surface of the slider bed, which is typically formed from steel or other rigid material.
An endless belt may be made by joining opposite ends of a belt material. Belts are often given a one or two-sided coating to provide certain desirable characteristics to the belt. Accordingly, different materials with different characteristics may be used for the coating. For example, various thermoplastic materials, such as PVC or polyurethane, are used for coating a belt for use in conveying systems.
The action of the belt passing over the rollers or across the slider bed generates friction between the bottom surface of the belt and the surfaces of the rollers or the slider bed. Efforts have been made to reduce this friction in order to reduce the power consumption required to drive the belt, friction-induced heating, and friction-induced noise. Reducing the friction can also enhance the operational life of the belt. It is known to reduce the friction of a belt through the use of lubrication on the bottom surface of the belt, and there are several known lubricants and associated methods. The underlying construction of the belt can also affect the resulting friction.
In addition, belts for use in certain applications must meet defined durability and flammability criteria. For example, a belt for use in an airport baggage conveyor system must be puncture and tear resistant and non-flammable. The defined criteria and test methods for belts in the U.S. are specified in ASTM D 378, “Standard Test Methods For Rubber (Elastomeric) Belting, Flat Type”, which covers the procedures for evaluating the physical properties of flat conveyor belting, including flammability. Meeting the flammability requirement of ASTM D 378 necessitates applying a flame retardant coating to the belt. However, it has been found that the non-flammable coating can prevent absorption of lubricant coatings.
For the foregoing reasons, there is a need for a belt with a reduced coefficient of friction for use, for example, in a conveyor system. The new belt should be able to meet desired criteria for operability and functionality in a preferred application.